To obtain a sealant which exhibits excellent resistances to soldering heat and moisture in the surface mounting of a semiconductor device by compounding an arom. polyepoxy compd., a specific phenol resin curative, an inorg. filler, and a cure accelerator.

This epoxy resin compsn. for semiconductor sealing is prepd. by compounding an arom. polyepoxy compd., a phenol resin curative contg. 30-100wt.% curative represented by the formula (wherein R is H, an alkyl, or halogen; and (n) is 0-10), an inorg, filler, and a cure accelerator. Pref. the epoxy compd. is of a phenol novolak type, a cresol-novolak type, or a bisphenol type, and when the compsn. contains the filler in an amt. of 80-90wt.%, the compd. is pref. a crystalline one, such as of a biphenyl type or a bisphenol type. The compsn. is used for sealing a thin package of a large-size semiconductor integrated circuit, exhibiting a high reliability of resistances to cracks and moisture at the soldering step.